//  公用rem.js
(function (doc, win) {
    var docEl = doc.documentElement;
    var resizeEvt = "orientationchange" in window ? "orientationchange" : "resize";
    var recalc = function () {
        var clientWidth = docEl.clientWidth;
        if (!clientWidth) {
            return;
        }
        if (clientWidth >= 750) {
            docEl.style.fontSize = "100px";
        } else {
            docEl.style.fontSize = 100 * (clientWidth / 750) + "px";
            // docEl.style.fontSize = 100 * (clientWidth / 375) + "px";
        }
    };

    if (!doc.addEventListener) {
        return;
    }
    win.addEventListener(resizeEvt, recalc, false);
    recalc();
    doc.addEventListener("DOMContentLoaded", recalc, false);
})(document, window);
/* 640为设计师设计稿的像素宽
var iWidth=document.documentElement.clientWidth  //getBoundingClientRect().width;
 iWidth=iWidth>640?640:iWidth;
 document.getElementsByTagName("html")[0].style.fontSize=iWidth/6.4+"px";
 */